Question : In the modern periodic table, 'A' and 'B' are two elements belonging to first and seventeenth group respectively and both of them belong to the third period. Write their electronic configuration. Which of them is a metal? Why? Write the chemical formula of the compound obtained when these two elements react with each other.

Question : In the modern periodic table, 'A' and 'B' are two elements

1.	Question : In the modern periodic table, 'A' and 'B' are two elements belonging to first and seventeenth group respectively and both of them belong to the third period. Write their electronic configuration. Which of them is a metal? Why? Write the chemical formula of the compound obtained when these two elements react with each other.
Answer» Solution :The two elements BELONGS to first and seventeenth GROUP and third period is .A.. SODIUM (NA) and .B. - Chlorine (CI) Na : 2,8, 1 CI: 2, 8, 7 A(Sodium) will be the metal, because it has a single electron in its outer shell, which readily donates, creating a positively charged ion the Na cation. `Na^(+) + Cl^(-) to NaCl` When sodium reacts with chlorine to get sodium chloride.